Substrate processing includes various process steps, each performed by a set of substrate processing tools, which yield a micromechanical, microelectrical, microelectromechanical (MEMS), or nano-scale device. Substrate processing steps often include operations such as substrate washing, substrate coating, substrate etching, substrate baking, etc. A variety of substrate processing tools are used to perform the various substrate processing steps, including substrate etch tools for etching processes. Substrate etch tools include ion etch tools, sometimes referred to as Reactive Ion Etch (RIE) or Dry Reactive Ion Etch (DRIE) tools. Ion etch tools come in many varieties, including Inductively Coupled Plasma (ICP) systems and Surface Wave (SW) systems.
Ion etch tools may be used to perform many of the substrate processing steps, including patterning of coatings formed on the surface of the substrate, trench or feature formation, pre-treatment and post-treatment processes, etch. An ion etch tool generally operates by forming a plasma field in a substrate processing chamber. The plasma field contains ions which interact with the surface of the substrate in various ways. Additionally, the plasma may include radicals in some cases, which may react with the surface of the substrate in other ways. The plasma field is formed by charging a gas chemistry with RF energy from an RF energy source.
In RIE systems, the substrate rests on a bias electrode which is charged by a second power source, commonly referred to as a “bias source.” The bias source may supply energy for accelerating the electrode in the direction of the surface of the substrate at a certain kinetic energy level. When the ions and/or radicals strike the surface of the substrate, they interact with the surface of the substrate. For example, the ions may strike the surface of the substrate and thereby remove portions of the surface of the substrate for patterning or material removal. Many other processing steps may be performed on the substrate in similar fashion and by similar systems.
Certain processing objectives are to be achieved in each processing step. Processing objectives include etching to a predetermined depth, etching features of a predetermined size, etching one material with a predetermined selectivity to another material, etc. In prior systems, the processing settings are entered prior to initiation of the processing step. The settings may be changed or a subsequent step, but that typically requires stopping the first processing step, possibly removing the substrate from the chamber, modifying the settings and initiating the new processing step. Such a process is often time consuming and may result in low yield rates, contamination of the substrate, delays, and additional costs. Additionally, prior processing systems do not have the flexibility to dynamically alter processing parameters.
Furthermore, industry drive toward smaller feature sizes has highlighted processing problems during gate etch. Non-volatile polymer is an etch by-product that deposits on the chamber wall, that may be desorbed into the plasma during the etch process, and that may be deposited back on to the wafer in the form of a film. In systems where feature size objectives are greater than 25 nm, the film does not block features, but in sub-25 nm systems, the film may obstruct or otherwise degrade the features.